1. Field of the Invention
The present invention relates to a method for oxidizing a hypophosphite ion, more particularly to a method for oxidizing a hypophosphite ion to a phosphite ion.
2. Description of the Related Art
As is well known in the art, a hypophosphite ion is used in a wide range of fields such as electroless nickel plating, catalysts, reducing agents, metal surface treatment, and pharmaceuticals.
In recent years, there has been a demand for elimination of phosphorous compounds as they are factors behind the eutrophication of lakes, swamps, and other parts of the environment. Along with this, some regions have imposed restrictions on the discharge of phosphorus.
As one of the methods of treatment of such phosphorus compounds, an effective method of treatment of a hypophosphite ion contained in the waste liquor of electroless nickel plating and the waste liquor of manufacturing processes of hypophosphoric acid, but as of now no effective methods of eliminating the hypophosphite ion has been found. Therefore, at present, studies are being made of methods of oxidzation for oxidizing the hypophosphite ion to a phosphite ion or a phosphate ion and then eliminating these as metal salts.
For the oxidation of a hypophosphite ion, for example, there have been reports of, for example, (1) a method of oxidizing a hypophosphite ion by NaOCl at an acidic region, (2) a method of oxidizing a hypophosphite ion by electrolytic oxidation, (3) a method of oxidizing and eliminating a hypophosphite ion using copper salts, and (4) a method of oxidizing a hypophosphite ion by ultraviolet ray using an optical catalyst (for example, an anatase type titanium dioxide powder).
However, there were problems in the above-mentioned conventional methods of oxidation of a hypophosphite ion, such as the hazardousness of the processes and the high running costs and thus they were not satisfactory as a practical method.